Computing devices such as personal computers, laptop computers, tablet computers, cellular phones, and countless types of Internet-capable devices are increasingly prevalent in numerous aspects of modem life. As such, the demand for data connectivity via the Internet, cellular data networks, and other such networks, is growing. However, there are many areas of the world where data connectivity is still unavailable, or if available, is unreliable and/or costly. Accordingly, additional network infrastructure is desirable.
Some systems may provide network access via a balloon network operating in the stratosphere. Because of the various forces experienced by these balloons during deployment and operation, there is a balancing of needs between flexibility and stability of materials. For instance, during flight, these balloons may use changes in altitude to achieve navigational direction changes. As an example, a balloon may pump air into a bladder within the envelope which causes a shift in the center of gravity of the balloon, which in turn, causes the envelope to tilt to one side. In some examples, this tilt can be up to 60 degrees from vertical.
In cases where the balloons carry networking equipment or other devices powered at least in part by solar, the balloon may also include a solar panel. In such cases, while tilting the balloon, it is important to keep the solar panel oriented towards the sun. A despin mechanism may be used to torque the payload against the balloon. When in a tilted condition, rigid connection between the payload and the balloon, however, may lead to failure in the despin mechanism.
Typical joints are unable to meet the requirements of the high altitude balloons and thus may not be sufficient for continued use. For example, universal joints do not offer the required range of motion, having only 1 degree of motion, and have undesirable inflection points. They also tend to lack smooth transitions between angles and have a cantilever effect that may result in high stresses and possible breaking. While double universal joints can bend further than universal joint, double universal joints are still limited in the range of motion and are unable to support large axial loads such as those expected during tilt. Similarly, typically flex couplings and corrugated tubing such as that used in coolant hoses could be used, but may provide insufficient torque transmission between the payload and envelope and may not handle axial load as typically implemented. In addition, while a cable inside a flex coupling may be used, but manufacturing techniques presently available are not scalable to the number of balloons needed to support an entire network of balloons.